The original. Dvl is on track in one area that a "receiver" of some type on body armor may be worth experimenting with. However, there are too many variables that would not make it worth while, in my opinion. Body armor is not permanently attached to the wearer, and one size does not fit all.
That little gadget severely limits the shooter's ability to manipulate his weapon. I'd like to see someone in that little video demonstration fire that weapon in a combat zone, from the prone, over a piece of hard cover, around the side of cover from the weak side, etc, etc, etc.
That little gimmick will get people killed. I'd like to see him have to 'find dirt' in a hurry and fall on top of the damn thing. Besides shooting his foot off, he'll have a flail segment of his entire right side rib cage.